Control system



G. E. KING CONTROL SYSTEM Aug. 16, 196e Original Filed March 6, 1961FIG. 2

INVENTOR.

ARY E. KING ATTORNEY G. E` KING CONTROL SYSTEM Aug. 16, 1966 4Sheets-Sheet 2 Original Filed March 6, 1961 IN VEN TOR.

M n@ o EE SEM Bim n m@ n@ ARY E. KING m@ D w@ Y B u NQ ATTORNEY G. E.KING CONTROL SYSTEM Aug. 16, 1966 4 Sheets-Sheet 5 Original Filed March6, 1961 NVENTOR.

GARY E. KING Bv? ATTORN Y Aug. 16, 1966 G. E. KING 3,266,754

CONTROL SYSTEM 4 Sheets-Sheet 4 Original Filed March 6, 1961 INVENTOR.ARY E. KING BY f f/ f ATTORNEY 3,266,754 Ice Y Patented August 16, 19663,266,754 CUNTRGL SYSTEM Gary 1E. King, Wichita, Kans., assignor toBoeing Airplane Company, Wichita, Kans., a corporation of DelawareOriginal application Mar. 6, 1961, Ser. No. 93,686, now

Patent No. 3,197,157, dated July 27, 1965. Divided and this applicationJan. 10, 1964, Ser. No. 347,081

6 Claims. (Cl. 244-83) This is a division of Gary E. Kings parentapplication Serial No. 93,686, filed March 6, 1961 and entitled ControlSystem, now Patent No. 3,197,157.

My invention concerns aircraft systems for moving control surfaces andthe like. My system is adapted t0 selectively use one or another controlunit to move the same control surface. For example, in a V/STOL aircraftWith pivotally mounted wings, it may be desirable to convert a -controlsurface from use as an sileron, controlled 'by the stick in horizontalflight, to use in the manner of a rudder controlled by a rudder pedal invertical flight. In VTOL and other aircraft, mixing of control may bedesirable Vso that a control surface. will function partly as a rudderresponsive to rudder pedal movement and partly as an elevator responsiveto stick movement, as for example in the tail control surfaces of aV-tailed aircraft. In V/STOL systems having tilting wings, my systemprevents deflection of control surfaces responsive to wing pivotingwhile retaining normal control surface movement `by a first and/ or asecond control unit.

These purposes are accomplished through use of epicyclic trains. Toprevent control surface deilection responsive to wing pivoting, athree-gear epicyclic train is used. One element is driven by thecontrolling unit, eg., the stick, the second element is connected to thecontrol surface, and the third element is moved by a mechanism actingresponsive to wing pivoting. A similar yassembly is providedadditionally to shift control of the control surface, as lbetween astick and a rudder pedal, by the use of both a four-gear and athree-gear epicyclic train interconnected so that wing pivoting resultsin shifting between the two control units. A single compound epicyclicgear train could be used for this purpose, but for clarity and easierunderstanding of the system, the two-gear train system will bedescribed.

The problems which the invention solves include (a) the problem ofcontrol surface deflection responsive to wing pivoting, (b) the changein functions of control surfaces between horizontal and vertical flightof a pivotal wing aircraft, and (c) the general problem of mixingcontrol between two different control units.

In one form of V/STOL aircraft, one or more Wings are pivoted betweengenerally horizontal orientation in horizontal flight and generallyvertical orientation in more vertical ilight, as in take-oil andlanding. Control surfaces usually are operated by pulley and cablesystems. In such systems, a pulley may be located on the wings pivotalaxis in order to pass the pivotal joint of the wing to the fuselage.When the wing is pivoted, the control surface cable wraps around apulley some place in the system and the control surface is deflected. Itis an object of my invention to prevent such deection.

The system also should have other desirable characteristics such asreliability, simplicity, and low weight. Many connections may have to bemade lbetween the fuselage and the wing for various systems andtherefore a compact system is highly desirable, particularly if theaircraft wing is thin. It is an object of my invention to provide thesecharacteristics in a system meeting the other objectives.

In converting between horizontal and vertical flight, control surfacesoften change function, i.e., etween aileron and rudder or betweenelevator and rudder.

Power plants also may have control functions in vertical flight, eg.,prop pitch.or engine speed of one or more engines may be varied. Thecontrol surface that is stick Controlled or a motor that is throttlecontrolled in horizontal Hight may need to be responsive to rudder pedaland stick movement, respectively, during vertical ight. During llighttransition when the wing may be, for exemple, in a 45 position, mixingof functions may be desirable. For example, a control surface may needto move partly responsive to rudder pedal movement and partly responsiveto stick movement. The mechanisms and systems that perform theseshifting and mixing functions should have the characteristics listedabove of reliability, simplicity, low weight and compactness and it willbe obvious after a study of the drawings and Written description thatthese objects 'best may be accomplished by integration with the systemjust previously described. It is an object of my invention to providesuch function changing and mixing capabilities in my control system.

Other types of aircraft than those mentioned have need for mixing offunctions of aircraft mechanisms. For example, a V-tailed aircraft mayhave control `surfaces with both rudder and elevator functions.v Thecontrol surfaces move responsive to rudder pedals and to fore and aftmovement of the stick. It is a further object v of my invention toprovide a system for mixing the response of a control surface or thelike responsive to more than one control unit. My control system isadaptable to interposition of trim motors in some of the mechanisms toperform trim functions and it is an object of my invention to adapt thecontrol system to provide this additional capability. The systemvshownand described has some applications other than use in pivoting wingaircraft, as will be understood by those working in the art afterreading the description, and it is an object of my invention to providea system useful in such other aircraft and non-aircraft applications.

v The structures of the invention, the problems to be solved, the methodof solution, and the objectives and advantages of my invention will befurther discussed below. The drawings of specific embodiments of myinvention include:

FIGURE l shows, in'schematical, fragmentary form, a simple planetarybevel gear train and associated system permittingpivoting of an aircraftwing ybetween horizontal and verticalpositions with neither controlsurface deliection nor feedback movement to the control unit;

p FIGURE 2 is an enlarged elevation view of the gear assembly taken online 2 2 of FIGURE 1;

FIGURE 3 is a side elevation View of an aircraft having two pivotalwings shown in horizontal position in solid lines and shown inV pivotedposition in dash lines. The 1general control system is shownschematically in dash mes;

FIGURE 4 is a plan view of the aircraft shown in FIGURE 3;

FIGURES is `a view showing schematically a system for preventing'control surface deection due to wing tilting and for changing or mixingcontrol surface function responsive to wing tilting;

- `FIGURE 6 schematically shows changing between or `mixing of elevatorand rudder controls for the same control surface;

FIGURE 7 is a view similar to FIGURE 6 in which propeller blade angle orpitch normally controlled by a manual control cable is convertible tostick control during vertical ight; Y

FIGURE 8 is a plan view of a shifter mechanism operable by wing pivotingto shift response of a control surface from one control unit to another;

FIGUREV 9 is a perspective View of one shifter means in a positionoperable to transfer motion;

FIGURE is similar to FIGURE 9 but shows the shifter mechanism in laposition inoperable to transfer motion; and

FIGURE ll is a perspective schematic of a control system utilizing myinvention to rachieve elevator and rudder control iu a V-tail aircraft.

The description of the invention will have the following order: (a) adescription of a type of V/STOL aircraft, (b) a description of Ia simplesystem for preventing control surface deflection during wing pivoting,(c) a description of a more complex system including changing and mixingcontrol functions, and (d) a description of a control system for acontrol surface of a V-tail aircraft.

Pivoling wing aircraft One basic problem to which the invention isaddressed is the provision of a control system for a control surface ona wing operated by mechanical motion transmitting means from .a controlunit in the fuselage, the wing being mounted on the fuselage to pivotabout a pivotal axis generally longitudinal of the wing and transverseof the fuselage. The control surface will pivot relative to the wingresponsive to pivoting of the wing relative to the fuselage unlesscompensating means are interposed in the mechanical motion transmittingmeans. The term mechanical motion transmitting means is used todistinguish hydraulic and electrical control means wherein this problemis not present. More broadly, the problem is the control of anadjustable member mounted on a first body which is pivotally mounted ona second body, the adjustable member being operated Iby a mechanicalmotion transmitting means from a control unit on the second body.

FIGURES 3 and 4 indicate one type of pivoting wing aircraft, one havingforward .and rearward wings 16, 18, both of which are pivotable aboutthe axes of pivotal joinder means 19 with fuslage 10. Fuselage 10 ismore similar to conventional aircraft than the wing and tail structures.A vertical stabilizer 12 has a rudder 14. In vertical flight the rudderwill be relatively ineffective to control flight di-rection and yaw.Wing 16 is located far forward and wing 18, in a. rear position, actspartly as a horizontal stabilizer. The control surfaces on rear wing 18function partly Ias elevators. The aircraft controls, i.e., stick andrudder pedals, a-re symbolized by a box at 21. The mechanisms of thepresent invention, including epicyclic gear trains, for compensating forwing pivoting in the control system and for changing from one controlunit to another in controlling control surfaces and propeller pitch, aresymbolized by boxes Forward wing 16 has control surfaces A, B, C and D,and rear wing 18 has control surfaces E, F, G and H. According t-o thedesign selected, in horizontal flight any of these surfaces can actpartly as ailerons governing roll, all can act as flaps, and any of therear control surfaces E, F, G and H can act as elevators. Of course somecontrol surfaces will be more effective than others for these functions.According to one design, control surfaces A, D, E and H Iare used asailerons and flaps in horizontal flight, control surfaces F and G areused as elevators and flaps, and surfaces B and C are used only asflaps.

In vertical flight control surface functions change.

,For directional control, surfaces A, B, E and F are pivoted aftresponsive to right pedal and surfaces C, D,'G and H are pivotedforward. Responsive to left pedal, surfaces A, B, E and F are pivotedforward and surfaces C, D, G and H are pivoted aft. Rudder 14 preferablymoves responsive to movement of the rudder pedals in lall modes but itseffectiveness decreases during transition from normal flight to verticalflight. Control in VTOL 'flight is also exercised through the powersettings of engines 20 and through change in propeller blade pitch.

VThis control is exercisable, according to the particular design, bystick and rudder pedals. The mechanism of the present invention,including the planetary gears, are usable to shift between regular andVTOL controls of engine power and propeller pitch, as will be understoodfrom the description below.

Control during STOL and transitional flight with small angles of wingpivoting may be similar to regular flight in most respects, although itmay be modified. Surfaces F and G pivot upwardly responsive to rearwardmovement of the stick and p-ivot downwardly responsive to forwardmovement of the stick. Surfaces E and A pivot upwardly and H and D pivotdownwardly responsive to right stick, and E and A pivot downwardly and Hand D pivot upwardly responsive to left stick.

Control surface deflection due to wing pivoting Use is made in thepresent system of epicyclic trains. One type is shown in FIGURE l andanother in FIG- URE 5. The assemblies are described hereafter as beingmounted in the fuselage, particularly because of space availability,although they could be mounted in the wing. According to the definitionof epicyclic trains, one gear or comparable element moves about theperiphery of another. An epicyclic train has the capability ofdifferential output motion and the present system utilizes thatfunction. The epicyclic trains shown in FIGURE l and at the left inFIGURE 5 are three-gear systems whereas the train shown at the right inFIGURE 5 is a fourgear sys-tem. The three gears at the left in FIGURE 5are a sun gear, planet gears and a ring gear, whereas at right in FIGURE5 the gears are .a sun gear, compound planet gears and two ring gears.The planet gears are not used directly for the input and output ofmotion. The pivotal input-output elements are the sun gears, the ringgears, and the carriers supporting the planetary gears in FIGURE 5, andthe two side bevel gears and the support for the third centralintermeshing bevel gear in FIGURE 2.

`Referring to FIGURES l and 2, wing 22 is mounted on -a fuselage topivot about an axis 214 between the full line horizontal position andthe dash line vertical position. The wing pivot axis 24 shown is notwithin the wing envelope in side view, although it could be in otherdesigns. A pivotal control surface 26 on wing 22 has an elevatorfunction and is responsive to fore and aft pivoting of stick 28. Stick28 has a pivotal support 30 and is biased toward a neutral position by aQ-spring 32. Normal motion transfer means between a stick and a controlsurface would be a straight cable run. In my invention an epicyclictrain 34 is interposed in the system and connects with ca'bles 36 and38. Cable 36 is pivota-lly secured to stick 28 at opposit-e sides ofpivot 30, and wraps around a pulley 40 of the epicyclic train 34. Cable38 wraps around pulley 42 of train 34 and around pulley 44 on wing pivotaxis 24. Motion is then transmitted by cable `46 wrapped about pulley 44to control surface 26. Cable 46 is attached to control surface 26 onopposite sides of the control surface hinge 48, as at 5t), 52. Cable 46is extending from pulley 44 to control surface 26 in wing 22 may passabout several pulleys which are not shown. The principles of the presentinvention can be used with mechanical motion transmitting other thancables, such as linkages `of rigid stock, but cables have been foundmost satisfactory, partly in weight savings, in most aircraftapplications where mechanical motion transmitting means are needed forlong runs.

1Pivoting of wing 2Q. from the full line horizontal position to the dashline vertical position as shown in FIG- URE l will wrap cable 46 aboutpulley 44 and, unless compensated, will deflect control surface 26 orfeed back movement to control stick 28. This deflection is avoided byuse of the epicyclic train of the present system as explained below.

Epicyclic train 34 has a base 6-2 having a bearing 64 supporting a firstbevel gear 68 connected to pulley 40,

and a second bevel gear 70 connected to pulley 42. Meshed with sidebevel gears 68, 70 is a central planet bevel gear 7,2. A support 74rotatably supports gear 72 land is free to -pivot about axis 66 ofpulleys 40, 4-2 and gears 68, 70. Planet gea-r 72 is supported by .abearing, not shown, and is secured by a nut and washer assembly 75. Gear'72 is free to rotate on its axis and to travel about the faces of sidebevel gears 68, 70. Support 74 is pivotally supported by paired arms 79journaled on the shafts for pulleys 40, 42. The support include saradially extending Iarm 76 for input of moti-on to the axis of `gear 72.Support 74 corresponds to the spider carriers in the epi- .cyclic trainsof FIGURE 5. Motion to arm 76 is imparted by a link 78 having one endpivotally connected to arm 76 at 8K1 and having its other end connec-tedto a pivot 89 on wing 22. The system including support 74, arm 76 andlink 78 may be termed iwing pivoting compensating means.

The operation of the FIGURES l and 2 systems is as follows: Controlmovement from the control unit, stick 28, is transmitted to move controlsurface 26 by action of 'cable 36 to rotate gear 68. As arm 76 isstationary except when the wing is bei-ng pivoted, rotation of bevelgear 68 merely rotates planet gear 72 about its axis, resulting inopposite rotation of bevel gear 7l) thereby irnparting movement to cable38. Th-is motion is transmitted t-hrough pulley 44 to cable 46 whichmoves control surface 2.6.

Although the system is operative to accomplish normal control surfacemovement through movement of stick 28 during Wing pivoting, let it beassumed for simplicity of description of the Wing pivot-ing compensatingmeans that control stick 28 is not being moved during wing pivoting. Ascontrol surface 26 is to remain in the same position relative to wing 22it has when wing pivoting commences, which may be in neutral ordeflected position, wrapping of cable 46 about pulley 44 must not occura-nd, therefore, pulley 44 must be rotated in the direction of wingmovement, e.g., pulley 44 is stationary relative to wing 22. This wouldfeed movement back to stick .'28 through cables 38, 36 if the motionwere not compensated in gear mechanism 34, and such stick movement mustnot occur.

As cable 38 moves as pulley 44 pivots with wing 22,

evel gear 70 rotates. Unless middle gear 72 walks around the side gears,bevel gear 68 will rotate and deflect stick 28. Planetary gear 72 doeswalk around the side gears as it has movement imparted thereto by link78 moving with wing 22. It will be understood, therefore, that deectionof the control surface or the stick will not occur provided the numberof gear teeth in the bevel gears, the size of pulleys 44, 42, thelengths and angles of the members such as arm 76 and link 78, and theplacement of the parts are such that the compensating movement ofplanetary gear 72 is right. Provision of these relationships is astraightforward design problem and need not be further detailed in thepresent disclosure. To describe the action in another way, .stick 28 isspring biased to a neutral position. Link 78 inputs motion to train 34during wing pivoting and this motion is fed to cable 38 rather than tocable 36 because of the spring resistance of the stick. Motion of cable38 rotates pulley 44 in an amount equal to the tendency of controlsurface cable 46 to wrap around pulley 44 in the .absence of thisrotation of pulley 44, whereby control surface 26 is not deflected bythe wing pivoting action.

The system also has provision for control surface trim, the trimfunction being the act of moving control surface 216 for trim purposeswithout alfecting the centered or neutral position and normal action ofstick 28. A trim motor 9i), interpositioned in link 78, is operable toextend or retract link 78. Motor 90 may be of any tyrpe, e.g.,electrical or hydraulic, and preferably would be an electrical systemi-n which con-trol of extension and retraction of link 78 is exercisedthrough a switch on control stick 28 and/ or signals from an autopilot.For example, extens-ion of lin-k 78 through operation oct trim motor 90will move planetary gear arm 76 counterclockw-ise as viewe-d. Forcontrol stick 28 to remain stationary, gear 70 and pulley 42 must rotatecounterclockwise. This movement is transferred through cable 38, pulley44, and cable 46 to deflect control surface 26 upward.

Changing and mixing control As earlier indicated, `a number of controlunits 21, such as stick, rudder pedal and throttle, act to move rudder14, control surfaces A, B, C, D, E, F, G, and H, engine fuel feed, andpropeller pitch control for engines 20. During transition betweenhorizontal and vertical flight, these functions variously are changedand/or mixed. Mixing is defined as the response of a control surface orthe like to more than one control unit at one time. Depending on design,mixing may be in equal or unequal proportions between the two controlunits. Responsiveness will be less during mixing than at other timesunless specifically compensated by the design.

Epicyclic gear train assemblies, such as the system 162 in FIGURE 5, areused both to compenate for wing pivoting and to mix or change betweencontrol units. Assemblies 102 may be centralized or located near thepivotal joints 19 between wings and fuselage. If two control surfacessuch as F and G are to have the same movements, a single system such as102 will suffice for both but they may be divided. In FIGURES 3 and 4,there are four locations 23, shown schematically, of epicyclic geartrains 102 but this may be varied according to design selection and therequirements of the particular aircraft.

In FIGURE 5, system 102 has an output in the form of a cable to acontrol surface, which, for example, operates as an aileron controlledby stick in normal flight and is controlled by rudder pedal in verticalflight. Cable 120 Wraps about a pulley 124 centered on the wing pivotaxis 126 in the same manner that pulley 44 has its center 24 on the wingpivot axis in FIGURE 1.

A four-gear epicyclic train 130 has a sun gear 132, a pair of ring gears134, 136, a plurality of planet gears 138 engaging the sun gear and thering gears, and a spider carrier 140 supporting the planet gears.Although pulleys are associated with the sun and ring gears and carrier,for simplification the cables are shown as directly connecting to cableand other imput-output elements. It may be assumed that the cables wraparound identical diameter pulleys juxtaposed to these elements. AlthoughFIGURE 5 shows epicyclic train 130 having dual diameter planet gears 138engaging ring gears of different diameters, this selection is forclarity of illustration, to avoid superimposing identical diameterparts, and planet gears 138 may not have dual diameters and ring gears134, 136 may have equal diameters. As two of the input-output elementsof three-gear train and four-gear train 130 merely transfer movementbetween the trains, a Vcompound train having ive input-output elementsis equivalent, i.e., the assemblies could be the same except for sharingthe same sun gear. The two train system was selected for clarity ofdescription. In any case, the epicyclic train means has but fiveinput-output elements `transferring motion external of the train means.

Train 130 may be best understood by comparing it to the structure ofFIGUE l as most elements and functions will be the same. Cable 141,connecting pulley 124. to carrier 140, serves the same function as cable38 connecting pulley 44 to pulley 42 in FIGURE 1. Extendible link 144,trim motor 146 and arm 148 extending from ring gear 134 in FIGURE 5,comprising wing pivoting compensating means, have the same function aslink 78, trim motor 90, arm 76 and support 74 for planet gear 72 inFIGURE 1. Cable 150, connected to the stick (not shown) and to ring gear136, and feedback cable 152 connecting sun gear 132 and sun gear 162 ofthree-gear epicylic train 160, next to be described, have partly thesame function as cable 36 connecting bevel gear 68 to stick 28 in FIGURE1.

The second assembly in system 102 is a three-gear epicyclic train 160having a sun gear 162, a ring gear 164, and a plurality of planet gears166 supported by a carrier 168. A shifter arm 174 extends from carrier168. The purpose of shifter arm 174 is to convert, through a shiftermechanism to be described later, from control of the control surface asan aileron by cable 150 from the stick (responding to stick sidewaysmovement), to control by movement of rudder control cable 170 from therudder edal.

p Following a similar operational cycle to that of FIG- URE 1, cable 182moves as the control stick is moved. Cable 182, operating through theshifter mechanism, actuates cable 150 thereby rotating ring gear 136.Ring gear 134 is fixed because of its attachment to a pivot 173 on thewing. If ring gear 136 rotates clockwise, planet gears 138 walk aroundring gear 134 in a counterclockwise direction, while rotating on theiraxes clockwise. This rotates carrier 140 counterclockwise, therebymoving cable 141, rotating pulley 124, and moving cable 120, therebymoving the control surface.

Simultaneously, sun gear 132 is rotated counterclockwise by planet gears138. Sun gear 132 is connected to feedback cable 152, the movement ofwhich will rotate sun gear 162 counterclockwise. Ring gear 164 cannotrotate at this time for it is connected to cable 170 which cannot movein this position of the design shown in FIG- URE 8. Since ring gear 164cannot rotate, planet gears 166 rotated by sun gear 162 will walk aroundring gear 164 counterclockwise while rotating clockwise on their axes.Carrier 168 will rotate counterclockwise, moving arm 174 which connectsto the shifter mechanism symbolized at 180 in FIGURE 5. The design ofshifter mechanism 180 is such that maximum control movement alone,through feedback cable 152, will not perform the shifting function. Theshifting function can be accomplished only by a selected angle of wingpivoting.

Presuming instead wing pivoting with no input of con- 'trol movement,ring gear 134 is pivoted clockwise with the wing because of theconnection of arm 148 and link 144. Planet gears 138 will walk aroundring gear 136 counterclockwise while rotating clockwise about theiraxes. This rotates sun gear 132 and carrier 140 counterclockwise.Carrier 140 and pulley 124, connected thereto by cable 141, will rotateat such a ratio to the wing rotational rate, that Wrapping of controlcable 120 about pulley 124 is prevented. Arm 174 is moved throughrotation of sun gear 132, movement of feedback cable 152 and action ofepicyclic train 160 in the manner as described above in normal controlstick movement but in an even greater movement suicient to perform acontrol shifting function in shifter mechanism 180 as will be laterdescribed.

Any movement of the control stick during wing pivoting, before shiftingto control by the rudder pedal, will act to deflect the control surfaceto the same extent that would occur if the wing were stationary.

If it be presumed that control of the control surface is shifted duringtransition from horizontal to vertical ight from response to stick cable150 to response to rudder pedal cable 170, cable 150 becomes xed andcontrol motion is from cable 170 rotating ring gear 164. Presumingshifter arm 174 to be stationary, rotation of ring gear 164 results inrotation of sun gear 162, movement of feedback cable 152, rotation ofsun gear 132, rotation of carrier 140, movement of cable 141, rotationof pulley 124, and movement of control surface cable 120.

Changing from control surface movement by stick cable 150 to controlsurface movement by rudder pedal cable 170 is accomplished .by shiftermechanism 180. Shifter mechanism 180 will be detailed in connection withFIG- URES 8, 9, and l0 but are schematically indicated in FIGURE 5.

Pivotal bodies 181 for cables 182 and 150 and -pivotal bodies 183 forcables 186 are used in FIGURE 5 to represent more complex assemblies inFIGURE 8 in which the pivotal centers shift relative to the points ofattachment of the cables. These pivot points are represented as a, b, cand d. The effective pivot point is at b for pivotal bodies 181 and at dfor pivotal bodies 183 in the full line position of shifter mechanism180, before shifting. The effective pivot point is at d for pivotalbodies 181 and at b for pivotal bodies 183 in the dash line position ofshifter mechanism 180, after shifting.

When the pivot point of pivotal body 181 is at b, before shifting, forceapplied through cable 182 from the stick results in pivoting of the bodyand application of force to cable 150. When the pivot point of pivotalbody 181 is at d, after shifting, force applied through cable 182 fromthe stick results in pivoting of the body but no application of force tocable as the cable attachment point is substantially aligned with theaxis of pivoting. Spring means acting on pivotal bodies 181 may be usedto prevent slack in cable 182 when, in shifted position, the pivotalaxis is at d. Similar to the above, rudder pedal cable 186 will notapply force to cable 170 when the pivotal axis of body 183 is at d, andcable 186 will apply force to cable when the pivotal axis of body 183 isat b.

Mixing of stick and rudder pedal is illustrated by pivotal axis positionc. If the shifter mechanism is operated to position the pivotal axes ofboth bodies 181 and 183 at c, both the stick, operating through cable182, and the rudder pedal, operating through cable 186, will operate tomove the control surface. Note that the control surface is lessresponsive to stick cable 182 if the pivotal axis of pivotal body 181 isat c rather than at b. Such mixing normally would occur at someintermediate wing position, i.e., 45, between horizontal and verticaldisposition. If such mixing is undesirable and it is desired to shiftinstantaneously between stick control and rudder pedal control of thecontrol surface, this can be provided by one of various commonmechanical devices, i.e., having a lost motion connection betweenshifter arm 174 and following mechanism and having a spring in theconnection so that the mechanism is thrown Ibetween stick and rudderpedal control extreme positions.

FIGURE 6 brieiiy indicates mixing between elevator and rudder controls,e.g., the stick and the rudder pedal, for a control surface normallyoperating as an elevator and operating in vertical flight as a rudder.For convenience in comparison with FIGURE 5, the comparable parts aregiven reference characters 15G', 170', 181', 182', 183 and 186. Onlythree pivotal axes a, b and c for bodies 181' and 183 are given toindicate absence of a mixing position. (Pivotal axes a are theoreticaland are not used in the FIGURE 5 and FIGURE 6 operations described,although they could be used for lost motion positions in the same manneras point d in FIGURE 5 and point c in FIGURE 6.)

FIGURE 7 indicates an arrangement similar to FIG- URES 5 and 6 by whichcontrol of propeller blade angle, normally responsive to a blade anglecontrol cable 182", is converted to stick control during verticalflight. For convenience of comparison, functional equivalents of thatshown in FIGURE 5 are given the reference characters 150, 170, 180, 181,182, 183 and 186". If it is desired at all times to retain control ofblade angle through control cables 182, the shifter mechanism can actonly on the pivotal axes of pivotal bodies 183 and the pivotal axes ofbodies 181 can remain at b. This is illustrated in FIGURE 7 in whichshifter mechanism 180H operates only on pivotal bodies 183".

Shifter m echan ism Various mechanisms may be used for the shifterfunction and may be designed to provide or avoid mixing, to

shift between'control units at any'selected angle of wing pivoting, ormay add one control medium to another rather than complete substitution.FIGURES 8, 9, and l illu-strate one type of shifter mechanism usable inthe FIGURES -7 systems. Adaptation of the design to particular aircraftand systems requirements and peculiar-ities will be understood by thoseskilled in the art.

FIGURE 8 shows somewhat schematically the shifter mechanism 180 used toperform the shifting functions heretofore explained. Four structurallyidentical shifter devices 184, 185 are shown in FIGURE 8 in juxtaposedrelationship, operatively connected to one another by an articulatedshifting link 190. Shifter devices 184, 185 are similar to mechanismsshown in Patents 2,936,967-8. Shifter devices 185 are shown on theoutside and correspond to pivotal bodies 181 in FIGURES 5-7. Shiftermechanisms 184 are on the inside and correspond to pivotal bodies 183 inFIGURES 5-7. Devices 185 are shown in a motion transmitting positionwhile inner shifter devices 184 are shown in locked or non-motiontransmitting position. A pin 212 extending from shifter link 19t) andengaging an arcuate slot 214 in the end of shifter arm 174 provides thedesirable lost m-otion previously mentioned.

The parts of shifter devices 184, 185 will be given the same referencecharacters. Two arms 192, 194 are pivotally connected to structure at196, 198 respectively. The outer ends of arms 192, 194 are connected byan articulated link 200, one portion 202 of which is equal in length toarm 194. Control cables 182, 186, which may turn about grooved pulleys204, are pivotally connected to the end 208 of arm 194. Cables 150, 170,to the epicyclic train system, are pivotally connected to center joint210 of link 200.

The purpose of the shifter'mechanism as previously stated is to providemeans whereby a control surface can be changed from one control unit toanother during wing pivoting, i.e., an aileron can be changed from stickcontrol to rudder pedal control, or the controls can be mixed. In FIGURE8, the outer shifter devices 185 are shown in a position wherebyactuation of the control surface through cable 150 is accomplished bymovement of the stick through cable 182. lIf cable 182 is movedclockwise as viewed, cable 150 will move counterclockwise. The two innershifting devices 184 in the position shown will not transmit motion fromrudder pedal cable 186 to the cable 178 for the epicyclic gear train andthere can be no feedback to the rudder pedal through the sys-v tem. Therudder pedal is, however, free to operate in its normal manner. Pivotaljoints 198 may be spring biased to press arms 194 to prevent slack incable systems 182, 186 when devices 184, 185 are in locked position, orthe slack can be compensated elsewhere in the system.

With shifter means 185, 184 in the positions indicated by dash lines,the opposite to the above occurs, eg., cable 186 from the rudder pedalsis effective and cable 182 from the stick is ineffective. In aposition-intermediate the full and dotted line positions of shiftingdevices 185, 184, mixing would occur, eg., both cables 186 and 182 wouldbe effective. The responsiveness in this mixing condition depends ontrigonometrical and other relations but in the design'shown the responseto movement of cables 186, 182 would be less in mixed position than infull operating condition. Mixing can be substantially avoided if themechanism is adapted for delayed action and snap of pin 212 lfrom onelimit to the other limit of slot 214.

In the full line position of shifting means 18S in FIG- URE 8, movementof cable 182r'esults in pivoting movement of point 210 (to which cable150 is connected) about pivot 198. Pivot 198 can be said (a) to havelposition b of body 181 in FIGURE 5 when in the operating, -full lineposition in FIGURE 8, (b) to have position d of FIGURE 5 in thenon-operating dash line position in FIGURE 8, and (c) to have position cof the axis of body 181 -in FIGURE 5 in a position intermediate full anddash line positions in FIGURE 8. Pivot 198 does not move but the rest ofthe shifting means 185 move relative to pivot 198 t-o accomplish theaction symbolized in FIG- URE 5. In the dash line position of shiftingmeans 185 in FIGURE 8, it will be understood that pivoting of arm 194and portion 202 of articulated link 200, responsive to movements ofcable 182 to the stick, will not result in movement of cable as the end210 of cable 150 will be substantially aligned with the axis ofpivoting, axis 198.

It will be understood that suitable cable tension devices, slackadjustors and other miscellaneous control system hardware not shown willbe used in a working control system.

FIGURE 11 In some control systems, it is desired to feed two controlinputs into a system to be mixed into one output. An example of this isthe combined elevator and rudder functions of the two control surfacesof a V-tailed aircraft. In such configuration the control surfaces mustserve both rudder and elevator functions and must respond both to stickand/or rudder pedal movements. FIGURE ll` shows the adaptation of myepicyclic gear train system to this application. The new systeml isreliable, compact and of low weight.

FIGURE ll shows a conventional stick 216, yoke 234 to which the rudderpedals are secured, two three-gear differential control drums 224, 226,two tail control surfaces 250, 252, and cables interconnecting thesecomponents. The two control surfaces 250, 252 are in an upright Vpivoting aboutaxes 251, 253 as will be understood by those skilled inthe aircraft art. The entire system may be regarded as twointerconnected individual systems, one to each control surface,operating from a common stick and common rudder bar. The controlsurfaces, and the individual systems associated therewith, operateoppositely in rudder lfunction and operate together in elevatorfunction. Epicyclic trains 224, 226 are shown schematically and thecables are shown as connecting directly to gears and the like, althoughin practice there will be pulleys associated with the sun and ring gearsand carriers.

Considering first the elevator function, two cables 232, 234 areattached at one end at 218 to stick 216 on one side of the stick pivotalaxis 217. The other end of cables 232, 234 attach at 220 to the opposite4side of the sticks pivotal axis 217, thereby formingclosed loops.Cables 232, 234 are wrapped in the same direction about ring gears 222of the respective differential control drums 224, 226 so that ring gears222 are rotated in the same direction by the stick and the controlsurface cables 236 from assemblies V224, 226 are moved in the samedirection. Output cables 236 are connected to control surfaces 250, 252in the same sense so that, through the system just described, controlsurfaces 250, 252 move together up and down responsive to movement ofstick 216.

The rudder function system differs from the elevator function system inthat the cables 228, 230 are wrapped around the sun gears 233 of therespective drums instead o'f thering gears 222 with cable 230 wrappedclockwise and cable 228 wrapped counterclockwise. Thus, movement of therudder pedal yoke 234 produces rotation of the sun gears 233simultaneously, but in opposite4 directions. Output cables 236 beingwrapped in the same direction about pinionV gear carrier 240, movementof rudder pedal yoke 234 results in movement o-f one control surface250, 252 up and movement of the other control surface down.

There is no feedback in this system. To demonstrate this, let it beassumed that control surfaces 250, 252 are locked. If stick 216 is movedbackward, cables 232, 234 are moved rotating ring gears 222 clockwise.Carriers 240 could not rotate if the control surfaces were locked, s sungears 233 would have to turn counterclockwise. However, rotation of sungears 233 counterclockwise would put both cables 241 and 242 undertension in directions opposing one another, and no movement could occur.This proves that feedback would not occur in the control cycle whencontrol surfaces 250, 252 move responsive to the stick.

Both stick 216 and rudder pedal bar 234 can be operated simultaneouslyby differential action of epicyclic gear trains 224, 226. Assume thatstick 216 is moved forward at the same time that rudder pedal yoke 234is rotated counterclockwise responsive to right rudder pedal. Cables232, 234 would be pulled rotating ring gears 222 counterclockwise. Cable242 would be pulled by yoke 234 to rotate sun gear 233 of train 224clockwise, whereby the differential output to cable 236 from train 224would be the resultant movement of carrier 240 and could be zero. Cable230 would be pulled by yoke 234 to rotate sun gear 233 of train 226counterclockwise, whereby the differential output to cable 236 fromtrain 226 would be the resultant movement of carrier 224 and could notbe zero.

Having thus specifically described my invention, I do not wish to beunderstood as limiting myself to the precise details of constructionshown, but instead wish to cover those modifications thereof which willoccur to those skilled in the art from my disclosure and which fallWithin the Iscope of my invention, as described in the following claims.

I claim:

1. A control system in -an aircraft for a control surface controllingthe aircraft .about two axes operated by mechanical motion transmittingmeans from a first axis control unit and a second axis control unit,comprising: an epicyclic differential planet-ary gear train interposedin said mechanical motion transmitting means, ysaid train having a ringgear element, a sun gear element, and a planet carrier element, saidring gear element being connected by said transmitting means to saidfirst control unit, said sun gear element being connected by saidtransmitting means to said second control unit, said planet carrierelement being connected by said transmitting means to said controllablesurface, and said controllable surface being responsive to controlmotions of said control units and responsive to differential controlmotions of said control units being operated concurrently.

2. A control system for an aircraft having first and second controlsurfaces oper-ated by mechanical motion transmitting means from a firstand a `second control unit, comprising: a first and a second epicycli-cring gear and sun gear differential planetary gear train interposed insaid transmitting means, each train having two input elements and anoutput element, an input element of each of said trains being connectedby said transmitting means to one of said control units, `another inputelement of each of said trains being connected by said transmittingmeans t-o the other of said control units, the output element of each ofsaid trains each being connected by said transmitting means to acorresponding one of said control surfaces, and each of said controlsurfaces being responsive to control motions of one of said controlunits and being responsive to differential control motions of saidcontrol units being operated concurrently.

3. The subject matter of claim 2 in which the aircraft has a V-tail .andsaid control surfaces are twin surfaces of said tail mounted in Vconfiguration land each having both rudder and elevator functions, andin which said first control unit is a control st-ick and said secondcontrol unit is a rudder pedal yoke Operated by rudder pedals.

4. A control system in an aircraft comprising, tiltable control surfacemeans for controlling the aircraft about two axes, first aircraft axiscontrol means, second aircraft axis control means, ring gear means, sungear means, planet gear means meshing with said sun gear means and saidring gear means, carrier means carrying said planet gear means, firstcable means drivingly connected to said carrier means between the endsthereof and connected to said control surf-ace means at the ends thereofin such a manner as to transmit pivotal movement of said carrier meansto said tiltable control surface means for tilting the same, secondcable means drivingly connected to said rin-g gear means between theends thereof and connected to said first control means at the endsthereof in such a manner as to transmit pivotal movement of said firstcontrol means to said ring gear means and said planet gear means andsaid carrier means and said t-iltable control surface means, and thirdcable means drivingly connected to said sun gear means between the endsthereof and connected to said second control means at the ends thereofin such a manner as to transmit pivotal movement of said second controlmeans to said sun gear means and said planet gear means and said carriermeans to said tiltable control surface means.

5. A control system in an aircraft comprising, tiltable control surfacemeans for controlling the aircraft about two axes, ring gear means, sungear means, planet gear means meshing with said sun gear means and saidring gear means, carrier means carrying said planet gear means, firstmeans drivingly connected to said carrier means in such a manner as totransmit pivotal movement of said carrier means to said tiltable controlsurface means for tilt-ing the same, second means drivingly connected tosaid ring gear means for 'pivoting the same and transmitting pivotalmovement to said carrier means and said tiltable control surface means,Iand third means drivingly connected to said sun gear means for pivotingthe same and transmitting pivotable movement to said carrier means andsaid tiltable control surface means.

6. A control system in .an aircraft comprising, tiltable control surfacemeans functioning both as an elevator and a rudder, ring gear means, sungear means, planet gear means meshing with said sun gear means [and saidring gear means, carrier means carrying said planet gear means, firstmeans drivingly connected to .said carrier means in such a manner as totransmit pivotal movement of said carrier means to said tiltable controlsurface means for tilting the same, pilot operated pitch control meansdrivingly connected to said ring gear means for pivoting the same andtransmitting pivotal movement to said carrier means and said tiltablecontrol surface means, and pilot operated yaw control means drivinglyconnected to said sun gear means for pivoting the same and transmittingpivotable movement to said carrier means and said tiltable controlsurface means.

References Cited by the Examiner UNITED STATES PATENTS 2,271,509 1/ 1942Rouanet et al 244-83 2,574,916 11/1951 Gordon 244-86 2,697,567 12/1954Fiedler 244-83 FOREIGN PATENTS 20,049 1911 Great Britain. 580,715 9/1946 Great Britain.

MILTON BUCHLER, Primary Examiner. FERGUS S. MIDDLETON, Examiner. A. E.CORRIGAN, Assslant Examiner.

1. A CONTROL SYSTEM IN AN AIRCRAFT FOR A CONTROL SURFACE CONTROLLING THEAIRCRAFT ABOUT TWO AXES OPERATED BY MECHANICAL MOTION TRANSMITTING MEANSFROM A FIRST AXIS CONTROL UNIT AND A SECOND AXIS CONTROL UNIT,COMPRISING: AN EPICYCLIC DIFFERENTIAL PLANETARY GEAR TRAIN INTERPOSED INSAID MECHANICAL MOTION TRANSMITTING MEANS, SAID TRAIN HAVING A RING GEARELEMENT, A SUN GEAR ELEMENT, AND A PLANET CARRIER ELEMENT, SAID RINGGEAR ELEMENT BEING CONNECTED BY SAID TRANSMITTING MEANS TO SAID FIRSTCONTROL UNIT, SAID